The water resistance property of electronic devices is getting more and more important.
Historically, the Ingress Protection (IP) classification system has been used to describe water resistance for electronic devices.
FIG. 1 shows an example of a speaker device 10 according to prior art, which is designed to be water resistant, for example down to 1.5 meter under water, e.g. classified as IP×8 water resistant. In FIG. 1, a section of the speaker device 10 is shown. A diaphragm 16 of the speaker device is made of a water proof material and fastened to a housing of the speaker device 10. The housing comprises two parts, an upper part 12 and a lower part 14. At an opening 22 of the housing, a water permeable grill (not shown) is fastened. This means that water can enter the housing through the water permeable grill and put pressure on the diaphragm 16. But since the diaphragm is water proof, no water should be able to penetrate the diaphragm and come in contact with any water sensitive electronics below the diaphragm. An edge portion 20 of the diaphragm is fastened between the upper part 12 and the lower part 14 of the housing of the speaker device 10. A suspension 18, which is used as retaining means when the diaphragm 16 vibrates, typically has a convex design.
By the term “convex” should, in the context of present specification, be understood that the suspension curves outwards, towards the water permeable grill.
However, when the electronic devices may be worn at the wrist of a user, the IP classification is often not used, instead the Atmospheres (ATM) classification, which is the well established standard for water resistance among watches, is used.
Moreover, when the electronic device is wrist worn, the user is more likely to wear the electronic device when swimming, snorkelling and diving, thereby exposing the electronic device to a higher water pressure compared to regular portable electronic devices such as Smartphone's or Tablet computers.
The established classification of watches usually claims 5 ATM to be waterproof enough to use while swimming, and 10 ATM to be waterproof enough to use when snorkelling down to 10 meter water depth. 10 ATM means that depths down to 100 meters may be handled.
Consequently, it is advantageous if electronic devices, especially wrist worn accessories, are designed to sustain a water pressure of 10 Atmospheres. This puts very high demands on the entire construction of the electronic devices, but especially on acoustic components in the electronic devices.